2004 Grand Caravan radiator fans stopped working


#1

I have a 2004 Dodge Grand Caravan 3.8 engine with 110,000 miles. Check engine came on with a code PO480 and now my radiator fans will not come on.
Both fans are suppose to come on by one solid state relay that is mounted behind the grill in front of the radiator.

My scanner is old, I was able to get the code and it gave me some data. It showed engine temperature climbing normal with my scanner so I suspect my temperature sensor is working good.

I jumped the connector for fan power and both fans came on, so the fans and fuses are good.

I tried to put control power from the battery to the relay and it would not close the switch. I’m not sure what kind of power the relay should get, pulsed, 5v, 12v? Anyway it did not close, I went out and bought a new relay from Autozone, installed and no change.

I tried to measure relay control voltage at the connector and got 0 on my digital meter.

I ohm the wire from the relay to the integrated control module and have continuity. I believe there is still a wire from the intergrated control module to the power train control module, however I don’t know where the power train control module is?

I also returned the solid state relay back to Autozone in case it was a new defect, but still no change. Its just a relay, you would think I can put the correct voltage and it would close my contacts. Anyone know what the relay control voltage is? Or where the power train control module is located?

Anyone know what I’m missing, or where to go next? Any help would be greatly appreciated.

Is my old bud Tester still on this site?


#2

Hey Nick! Long time no hear!

The code indicates Cooling Fan 1 Control Circuit Malfunction.

The cooling fan circuit operates from the signal that the computer receives from the coolant temp sensor. The computer then supplies 5 volts thru the integrated control module to the fan relay. This causes the contacts to close which then supplies 12 volts to the fans.

If the 40 Amp fuse is good and the relay has been replaced, then look at the coolant temp sensor for the computer. If that checks out good, then there’s only two things that can prevent the fans from operating. And that is either the integrated control module,

or the ECU itself.

Tester


#3

Hey what’s it been 15 years?

I jumped 12 volts to the relay and cant get it to switch. Is it possible bad batch of Duralast relays?

My scanner shows engine temp at operating range, wouldn’t that mean temp sensor is good? Cant get behind it to ohm it out.


#4

You can only supply 5 volts to the primary side of the relay. Anything higher in voltage will fry the coil in the relay.

Look at the relay, and you’ll see what contacts are the primary side which goes to the coil of the relay, and the secondary side which are the contacts.

Now go to the relay socket, plug in a jumper wire for the secondary side of the relay. If the fans run, there’s either a problem with the relay, or a problem with the primary supply voltage to the relay.

To check for primary voltage to the relay, get the engine up to operating temperature. Then take a meter set it on 20 volts DC, and check for 5 volts supply voltage on the relay socket. If you don’t see 5 volts at the socket, then there’s problem with either integrated control module or the ECU.

Tester


#5

It turned out to be a bad wire from the PCM to the ICM.

Weird, don’t know how the wire can go bad, its all bunched up and wrapped up. I cut the wire and installed new wire from the PCM to the ICM and it fixed the problem.


#6

Good job. Thanks for the update.